Please refer to FIG. 1, in a full in-cell design, a common electrode (Vcom ITO) layer 201 needs to be divided into multiple (i.e., more than one) small rectangular blocks as sensing blocks 202, and then the sensing blocks 202 are connected to a drive circuit 204 by metal wires 203 and thereby a design of a self-capacitive touch panel is completed. In the design, the multiple sensing blocks 202 each need to perform a time-division multiplexing operation, i.e., work for a display function and a touch function in different time periods respectively. Therefore, it is needed to provide appropriate voltage waveforms to the sensing blocks 202 and related wires so as to meet the requirement.
Please also refer to FIG. 2, patterned metal wires (Metal3) 203 and source lines 206 of the touch panel all are overlapped with a black matrix layer 205 of pixels. Please refer to FIG. 3 and FIG. 4 together, the touch panel further includes a demultiplexer (Demux) used for controlling conduction and disconnection between a terminal of Source and RGB. In order to avoid generating a coupling effect between the metal wires 203 and the source lines 206, a loading of the touch panel is increased in need. Generally, in display and touch stages, the respective lines will be applied with voltages having voltage waveforms as shown in FIG. 4. That is, in the touch stage, when there is a touch happening, the source lines 206 and the demultiplexer will transmit a signal with a same waveform as that on the metal wires 203 (Vcom), so as to avoid generating the coupling effect.
Because in the touch stage, when there is no touch happening, the source lines 206 are in a state of low level (the demultiplexer is at a continuous high level at this time), which is equivalent to grounding, although the gate has been closed at this time. However, because a thin film transistor (TFT) has a certain leakage current, some of charges of a liquid crystal capacitance would leak through the source lines 206. Generally, multiple touch stages would be divided equally in a scanning time in a frame of image, which makes electricity leakage times of the respective touch stages be different, resulting in a problem of uneven brightness spots (Mura) or color difference occurred in the image.